Electric arc lamp



A 2, 1938. c. T. CROCKER 2,125,769

ELECTRIC ARC LAMP Filed Oct. 17, 1936 -Fig. 5. 37 3/ /p Inventor: ,g C lar-ence T Crocker; 36 //I His Attorheg.

Patented Aug. 2, 1938 UNITED. STATES ELECTRIC ARC LAMP Clarence T. Crocker, Daytona Beach, Fla., assignor to General Electric Company, a corporation of New York Application October 17, 1936, Serial No. 106,152

9 Claims.

My invention relates to are lamps, such as are used in connection with large searchlights, for example, and more particularly to an improved electrode feeding mechanism therefor.

In such are lamps it is desirable to have a variable speed feeding mechanism for advancing and retracting the negative carbon with respect to the positive carbon which is actuated in response to an operative condition of the arc. Such feeding mechanism may, for example, be actuated in response to the current flowing through the are 'or in response to the voltage across the arc. The feeding mechanism advances the negative carbon into engagement with the positive carbon upon initiation of operation of the arc lamp at a high rate of speed to strike the arc. Likewise, the negative carbon is retracted at a high rate of speed after the arc has been struck to quickly establish opera- 90 tion of the lamp. After operation has been established the feeding mechanism acts to maintain such operation. The rate of speed at which the negative carbon is adjusted to maintain satisfactory operation of the lamp is preferably a dependent upon the condition of the arc. For

example, if the negative carbon should be advanced or retracted only a small distance the adjustment is made at a low rate of speed; whereas, if such carbon is to be advanced or retracted so a greater distance the adjustment is preferably made at a greater rate of speed.

An object of my invention is to provide an improved mechanism for effecting a variable speed feeding of the negative carbon used for high inu tensity arc lamps.

Another object of my invention is to provide a feeding mechanism which will act to advance or retract the negative carbon, as operating conditions demand, at variable rates of speed depending upon the amount of adjustment required so that large adjustments are effected at proportionately higher rates of speed than the rates at which the small adjustments are effected.

For a better understanding of my invention,

together with other and further objects thereof,

reference is had to the following description, taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 is a perspective view of the carbonfeeding mechanism built in accordance with my invention; Fig. 2 is a side elevation of an arc lamp provided with a carbon feeding mechanism embodying my in- 55 ventlon, and Figs. 3, 4 and 5 are schematic diagrams indicating various operating positions of the adjustable cams employed in the carbon feeding mechanism.

Referring to the drawing, Fig. 1 illustrates in detail a portion of my carbon feeding mechanism which includes a drive-shaft l0 rotatably supported in suitable bearings II and I2 and two driven shafts l3 and I4 operatively connected to shaft 10 by means described hereinafter. Driveshaft I0 is driven at a predetermined constant speed by a motor l5 through a suitable speed reduction gearing l6. Driven shafts l3 and M are operatively connected to control the feeding of the negative carbon l1 and positive carbon 20 respectively, of the arc lamp, in a manner which will be better understood from av description of Fi 2.

In Fig. 2 the negative carbon I1 is carried by a supporting and feeding mechanism I8 of any desired construction which is operatively connected to driven shaft l3 through a suitable linkage l9. This mechanism is described in detail in my U. S. Patent No. 1,837,897, issued December 22, 1931. It will be understood that when shaft I3 is rotated in one direction mechanism l8 will be actuated to retract the negative carbon toward the positive carbon and when shaft I3 is rotated in the opposite direction the mechanism will be actuated to retact the negative carbon from the positive carbon. In other words, mechanism I8 is operable to vary the length of the are between the negative and positive carbons. The positive carbon 20 is carried on a supporting and feeding mechanism 2| of any desired construction which is operatively connected to driven shaft ll through suitable linkage 22. The mechanism 2! forms no part of the present invention. Any suitable mechanism may be used. The particular mechanism illustrated is described in detail in U. S. PatentNo. 1,594,067, Murphy and Hutt, issued July 27,- 1926. This mechanism continuously rotates the positive carbon and feeds it forward from time to time as required during the operation of the lamp. Carbon feeding mechanisms l8 and 2| are carried by 5 a standard 23 which is supported by a suitable base 24. Preferably base 24 is arranged to house the mechanism for actuating carbon feeding mechanisms l8 and 2|, shown in Fig. 1, and protects the mechanism from exposure to the weather. The driven shafts l3 and I extend from the base 24 throughthe upper cover thereof.

Referring again to Fig. 1, it will be observed that driven shaft I4 is directly connected to drive shaft I0 through bevel gears 25. The driven shaft I3 is normally disconnected from drive shaft II and is adapted to be connected thereto through clutches 26 and 21. For purpose of convenience, clutch 26 is referred to as a retracting clutch and clutch 21 as an advancing clutch since corresponding movements of the negative carbon are produced when the respective clutches are engaged.

Since these clutches are of similar construction, only one of them will be described in detail. The retracting clutch 26 includes an arm 26 rigidly secured. at its mid-portion, to drive-shaft II and is provided with a pin 29 at each end thereof for supporting pawls 30. A cooperating ratchet wheel 2| having attached thereto a bevel gear 22, in mesh with a similar gear 33 on the driven shaft-LI, is loosely carried by drive-shaft II. A spring biasing means 24 is interposed between each pawl 30 and arm 28 to urge the pawls into engagement with the ratchet wheel 3i.

Clutch 26 is provided with an operating cam 66 comprising a stationary portion '36, carried by hearing II, and a complementary movable portion 81, carried by a bracket 36. Preferably the portions 26 and 21 of the cam 35 are substantially semi-circular in shape and so positioned on either side of the drive-shaft III that when the cam occupies itsnormal or neutral position of adjustment the contour or the periphery of the cam is substantially a circle. Each of the pawls 36 is provided with a guide pin, attached to its free end. which rides on the periphery of the cam and follows the contour thereof.

It will be understood that the radii .of the two cam portions 66 and 31 are equal and sufficiently great to restrain pawls 26 from engagement with ratchet wheel 2i when the movable part 31 of the cam occupies its normal or neutral position of adjustment shown in Fig. 1. Further, it will be understood that when either guide pin 40 is riding upon the stationary cam portion 36 that the corresponding pawl 30, secured to the guide pin, can never engage the ratchet wheel 3i as such pawl is restrained and held in a semicircular path of travel of greater radius than the radius of the ratchet wheel. When a guide pin 46 is riding upon the movable cam portion 31 the corresponding pawl 20, operated by that 'pin, may or may not engage ratchet wheel ii.

depending upon the position of the movable cam portion 21 with respect to the stationary cam portion 66.

For a more detailed consideration of the clutch controlling action of cam 36, reference is had to Figs. 3 to 5 inclusive of the drawing. In these figures the drive shaft i6 and the ratchet wheel II are respectively indicated. The radii of the cam portions 36 and 31 are indicated by the distance'R, and the center of the movable cam portion 61 is indicated at C. The lower portion of the surface of radius It indicates the stationary cam portion 66, while the movable portion 31 of the cam is indicated as the upper portion of the surface of radius R.

From an inspection of Fig. 3, schematically illustrating the normal or neutral position of the cam. it is apparent that no portions of the semicircles of radius R intersect the circle indicating the ratchet wheels Ii; thus. when the cam occupies this posilton there can be no engagement between a pawl 26 and the ratchet wheel 2i. Accordingly, clutch 26' is in a disengaged position.

From an inspection of Fig. 4 schematically illustrating an adjusted position of the cam produced by a downward movement of cam portion 21, it is apparent that the upper semi-circle of radius R intersects the circle of wheel ii at points II'. Accordingly, a pawl 36 will engage ratchet wheel II when its guide pin 40 rides the movable cam portion 61, along the periphery thereof between points II.- When the cam occupies this position of adjustment the clutch will be engaged twice upon each revolution of drive shaft lli since there are two pawls employed in the clutch. Further, it will be understood that the ratchet wheel will be rotated an angular distance corresponding to twice the angular distance between points I--I' upon each revolution of drive shaft iii. In the position of adjustment illustrated the angle between points I--i0-I' is approximately thus the ratchet wheel would be rotated approximately 240 upon each revolution of drive shaft ill.

Also, it is obvious that the angle between points I-iliI' is a function of the downward displacement of the movable cam portion 21 and that the angular rotation of ratchet wheel 3i for each revolution of drive shaft I6 is thus a function of such displacement. In view of the fact that the drive shaft i0 is rotated at a predetermined constant velocity it will turn a known number of revolutions during any given time interval and with a given adjustment of the cam 31 the ratchet wheel 3i will be rotated a constant number of revolutions during the same time interval. Therefore, the average speed of rotation of the ratchet wheel is a function of the adjustment of the cam and can be varied by varying the adjustment of the cam.

Fig. 5 schematically illustrates the position of the movable cam portion 31 when a condition opposite to that of Fig. 4 occurs. The cam portion 31, when the condition illustrated in this figure occurs, lifts the guide pin 46 and pawl 30 farther from the teeth of wheel II but does not otherwise affect the operation of the mechanism. Furthermore, when this condition occurs the movable cam portion 63 of clutch 21, see Fig. 1, which corresponds to the cam portion 31 of clutch 26, is correspondingly lifted so that its surface is moved nearly to the shaft i0 and allows pawl 45 to engage the ratchet, wheel 46 in the manner just described for clutch 26.

The construction and principle of operation of advancing clutch 21 is similar to that of the retracting clutch 26. It is provided with a cam 6 I having a movable clutch portion 43 and a stationary portion 62. A ratchet wheel 46 is engageable by two pawls 65 which are controlled by guide pins 46 which ride on the surface of cam ll. cam portions 42 and 62, respectively, are displaced 180" with respect to the corresponding cam portions in the retracting clutch 26. That is, as illustrated in Fig. 1, the stationary cam por tion 42 in the, advancing clutch 21 is positioned at the top of the cam and the movable cam portion 43 is positioned at the bottom of the cam, while in the retracting clutch the stationary cam portion 36 is positioned at the bottom of the cam 25 and the movable cam portion 31 is positioned at the top of the cam. In clutches 26 and 21, stationary cam portions 36 and 62 are supported by bearings Ii and i2 respectively, while movable cam portions 31 and 63 are carried by the supporting bracket 36.

Due to the disposition of the movable cam portions 21 and 43 on opposite sides of drive shaft Ill and to the fact that these cam portions are carried by a common bracket 38, above de- The stationary and movable scribed, it will be understood that the clutches 26 and 21 are positively interlocked to prevent simultaneous engagement thereof. For example, when bracket 38 is moved upwardly cam 4| is contracted and clutch 21 is engaged, while cam is expanded and clutch 26 is further prevented from being engaged. On the other hand, when bracket 38 is moved downwardly, cam 35 is contracted and clutch 26 is engaged, while cam 4I is expanded and clutch 2'I ls further prevented from being engaged. The alternate engagements of clutches 26 and 21 act to drive shaft I3 in opposite directions of rotation to accomplish retracting and advancing, respectively, of the negative carbon.

The supporting bracket 38 is secured to a pivoted armature 50 of an electromagnetic device 5| provided with a solenoid 52 which is connected across the positive and negative carbons 20 and I8 and is therefore responsive to the arc voltage of the lamp. Adjustable spring 53 is provided to oppose the attractive force of the electromagnetic device upon the armature. The

armature 56 is pivoted by a pin 54 extending.

through one end of the electromagnetic device 5|.

The operation of the device is as follows: When the circuit is first closed across the carbons, "1e carbons being separated, full line voltage is npressed across solenoid 52 in the electromagnetic device 5|. The electromagnetic device 5| then attracts the pivoted armature 50 against the bias of spring 53, thereby swinging bracket 38 in an upward or counter-clockwise direction about the pivot of the armature 50. This motion of the bracket will adjust cams 35 and 4| provided in the retracting and advancing clutches. The movable cam portion 31 in cam 35 will be moved upwardly to expand the cam surface and further restrain engagement between pawl 38 and ratchet wheel 3| as illustrated in Fig. 5. The movable cam portion 43 in cam 4| will be simultaneously moved upwardly to contract the cam and permit engagement between the pawl and ratchet wheel 44 in clutch 21 in the manner illustrated in Fig. 4. The actual positions of the stationary and movable portions of cam 4| are inverted from those illustrated. This adjustment of cam 4| permits advancing clutch 21 to close. Rotary motion of drive shaft I0 is then transmitted through clutch 21 to driven shaft |3 causing the carbon feeding mechanism to rapidly advance the negative carbon into engagement with the positive carbon to strike the arc. Under these conditions the armature 50 moves the cam portion 42 to its innermost position so that the pawls engage the ratchet wheel during substantially the whole of each revolution of shaft I0 and the shaft I3 is therefore rotated at its maximum speed.

, As soon as the arc has been struck the voltage across the carbons will become substantially zero due to the engagement of the carbons. Due to the corresponding reduction in current, solenoid 52 can no longer hold the pivoted armature of the electromagnetic device 5| against the bias of spring 53 and the armature, and bracket 38 secured thereto, are swung in a downward or clockwise direction about the pivot of the armature 50 by spring 53. This motion of the bracket will act to move cam portions 35 and 4| to close the retracting clutch and open the advancing clutch. Under this condition the cam portion 31 is at first moved to its innermost position allowing pawls 30 to engage the ratchet wheel 3| for substantially the whole of each revolution of shaft I0 and therefore reverse shaft |3 at a maximum speed. This speed ,is. however, gradually reduced as the voltage of the arc increases because the armature gradually moves the cam portion 31 outwardly and thereby reduces the angle of engagement between the pawls 30 and wheel 3|.

The movable-cam portion 43 in cam 4| will simultaneously be moved downwardly to expand the cam and further restrain engagement between the pawl and ratchet wheel in clutch 21 as operatively illustrated in Fig. 5. The actual positions of the stationary and movable portions of cam 4| are inverted from those illustrated as previously noted. This adjustment of cam 35 permits retracting clutch 26 to engage or close. Rotary motion of drive shaft I0 is then transmitted through clutch 26 to driven shaft I3 causing the carbon feeding mechanism to rapidly retract the negative carbon from engagement with the positive carbon to draw the are.

As the negative carbon is retracted from engagement with the positive carbon the arc voltage between the carbons impressed upon solenoid 52 increases, causing the electromagnetic device 5| to attract armature 50 against the bias of spring 53. As the arc voltage increases armature 50 will be gradually swung, together with bracket 38, in a counter-clockwise direction about its pivot until an equilibrium position is obtained, at which position the attractive force exerted upon armature 50 by the electromagnetic device 5| will be balanced'by the:

bias of spring 53. When the armature 50 occupies this position of equilbrium, bracket 38 secured thereto will position cams 35 and 4| into their normal or neutral positions of adjustment as illustrated in Fig. 3, causing clutches 26 and 21 to be disengaged. It will be understood that the pivoted armature 50 will be moved from its position of equilibrium toward or away from solenoid 52 in response to operating conditions of the arc to effect adjustments of cams 35 and 4| which act to selectively engage clutches 26 and 21 to reposition the negative carbon, to maintain the distance between the positive and negative carbon a proper one to obtain satisfactory operating conditions.

Also, it will be understood that the amount of movement of armature 50 from its position of equilibrium will be proportional to the arc voltage and, therefore, proportional to the amount which the carbon should be adjusted to re-establish satisfactory operation conditions, and that as hereinbefore explained in connection with Figs. 3 and 5 the amount of this movement of the armature 50 will determine the rate of speed at which driven shaft I3 is operated to bring about the necessary adjustment of the negative carbon. Under ordinary conditions of operation of the lamp this movement will be slight and the rate of speed at which an adjustment will be made will be low as compared to the high rate of speed at which the arc is struck, as describe hereinbefore.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination in an arc lamp having a carbon and a carbon feeding mechanism for advancing and retracting the carbon, of means for actuating the carbon feeding mechanism comprising a drive member, a driven member operatively connected to said carbon feeding interposed between said members, said clutch mechanism being adjustable to eirect a variable average speed transmission between said mem-' bers, and means actuated in response to operating conditions of the are for selectively actuating said clutch mechanism to effect movement of said carbon for adjusting the clutch mechanism to vary the average speed transmission between said members.

2. The combination with an arc lamp having a carbon and a carbon feeding mechanism, of means for actuating the carbon feeding mechanism comprising a drive shaft, a driven shaft operatively connected to said carbon feeding mechanism and rotatable in either of two directions to feed the carbon forward and back means for clutching said drive shaft to said driven shaft to rotate the latter in either of said two directions including a forward and a reverse ratchet clutch, each clutch comprising respectively a pawl supporting arm fixed to said drive shaft, a plurality of pawls carried by said arm, and a ratchet wheel loosely carried by said drive shaft in driving relationship with said driven shaft, means for controlling the engagement of said pawls and said ratchet wheels ineluding adjustable cam members and means for adjusting ,said' can members responsive to an operating condition'oi' the 3. The combination in arc lamp having a carbon and a carbon feeding mechanism for advancing and retracting the carbon, of means for actuating the carbon feeding mechanism comprising a drive shaft, a driven shaft operatively connected to said carbon feeding mechanism, an advancing clutch and a retracting clutch interposed between said shafts, said clutches being selectively engageable to effect corresponding movements of said carbon, each of said clutches comprising a ratchet wheel loosely carried by said drive shaft and a member rigidly carried by said drive shaft provided with a pawl biased toward engagement with said ratchet wheel, an adjustable cam for each clutch for controlling the engagement of pawl and ratchet wheel therein, the cams being adjustable to permit such engagement only during a portion of each revolution of said drive shaft, means interlocking the adjustments of said cams to prevent such engagement simultaneously in both clutches and means actuated in response to an operating condition of the are for adjusting said cams for ratchet wheel and a pawl carried by said drive shaft adapted to engage said ratchet wheel, a clutch control cam for each clutch for effecting engagement and disengagement of the respective cooperating pawl and ratchet wheel to eflect clutching and declutching, means for interlocking said clutch control cams to prevent simultaneous clutching of said clutches and means mechanism and a reversible clutch mechanism responsive to an operating condition of the are for actuating said clutch control cams.

5. The combination in an arc lamp having a carbon and a carbon feeding mechanism for advancing and retracting the carbon, of means for actuating the carbon feeding mechanism comprising a drive shaft, a driven shaft operativeb connected to said carbon feeding mechanism, an advancing clutch and a retracting clutch interposed between said shafts, said clutches being selectively engageable to eifect corresponding movements of said carbon, each of said clutches comprising a ratchet wheel in driving engagement with said driven shaft, a pawl carried by said drive shaft biased toward engagement with said ratchet wheel and a clutch control cam for normally restraining said pawl from engagement with its cooperating ratchet wheel to effect declutching, said cam being adjustable to permit such engagement to effect clutching, means for interlocking said clutch control cams to prevent simultaneous clutching of said clutches and means responsive to an operating condition of the are for adjusting said clutch control cams.

6. The combination in an arc lamp having a carbon and a carbon feeding mechanismfor advancing and retracting the carbon, of means for actuating the carbon feeding mechanism comprising a drive shaft, a driven shaft operatively connected to said carbon feeding mechanism, an advancing clutch and a retracting clutch interposed between said shafts, said clutches being selectively engageable to effect corresponding movements of said carbon, each of said clutches comprising a ratchet wheel in driving engagement with said driven shaft, a pawl carried by said drive shaft biased toward engagement with said ratchet wheel and an adjustable cam for normally restraining the pawl from engagement with its cooperating ratchet wheel, said cams being adjustable to permit such engagement, means for adjusting said cams responsive to an operating condition of the are and means interlocking the adjustments of said cams to prevent adjustment thereof to effect simultaneous engagement of pawl and ratchet wheel in both clutches.

7. The combination in an arc lamp having a carbon and a carbon feeding mechanism for advancing and retracting the carbon, of means for actuating the carbon feeding mechanism comprising a drive shaft, a driven shaft operatively connected to said carbon feeding mechanism, an advancing clutch and a retracting clutch interposed between said shafts, said clutches being selectively engageable to effect corresponding mOVflgfflflN of said carbon, each of Isaid clutches comp ng a ratchet wheel in dri ement with said driven shaft, a page??? said drive shaft biased toward engagement with said ratchet wheel and an adjustable cam for normally restraining the pawl from engagement with its cooperating ratchet wheel, said cams being adjustable to cause a variable intermittent engagement between said pawl and ratchet wheel. the period of engagement being variable and responsive to the adjustment of said cams, and means for adjusting said cams responsive to operating conditions of the are.

8. The combination in an arc lamp having a carbon and a carbon feeding mechanism for advancing and retracting the carbon, of means for actuating the carbon feeding mechanisnr comprising a drive shaft, a driven shaft operatively connected to said carbon feeding mechanism. an advancing clutch and a retracting clutch interamuse posed between said shafts, said clutches being selectively engageable to effect corresponding movements of said carbon, each of said clutches comprising a ratchet wheel loosely carried by said drive shaft, a member rigidly carried by said drive shaft provided with a pawl spring biased toward engagement with said ratchet wheel and an adjustable cam-for normally restraining the pawl from engagement with its cooperating ratchet wheel, said cams being expansible to further insure disengagement of the pawl and ratchet wheel and contractible to permit such engagement and comprising complementary stationary and movable portions supported on opposite sides of said drive shaft, similar portions of said cams being disposed substantially 180 with respect to each other, the movable portions of the cams being carried by a support, said support being movable in one direction to simultaneously expand one of said cams and contract the driving pawl and a ratchet wheel which when moved efl'ects an advance of said carbon, means for continuously moving said pawl at a uniform speed, and means responsive to a potential across the arc efl'ecting an intermittent engagement between said pawl and said ratchet wheel, the proportion of the time of engagement to the time of disengagement between said pawl and said ratchet wheel being regulated by said means responsive to the magnitude of said are potential, whereby the rate of advance of said carbon is proportional to said arc potential.

CLARENCE T. CROCKER. 

